Vice President Biden and Paul Ryan debated at Centre College in Danville, Ky. / Pool photo by Michael Reynolds

by Catalina Camia , USA TODAY

by Catalina Camia , USA TODAY

The debate billed as the "Thrill in the 'Ville" between Vice President Biden and Paul Ryan on Thursday drew an estimated audience of 51.4 million people.

Nielsen, the ratings company, said Friday that draw was far short of the TV viewers who tuned in to Biden's matchup with Sarah Palin in 2008. Four years ago, the sole debate between the vice presidential nominees attracted 69.9 million TV viewers.

The Biden-Ryan debate was held at Centre College in Danville, Ky., and moderated by ABC's Martha Raddatz. Ten networks carried the faceoff on live TV. (The college's hometown helped provide the moniker for the debate.)

While the faceoff between the No. 2 men on the presidential tickets was far more lively than last week's Denver debate between Obama and Mitt Romney, the top of the ticket had a bigger TV audience. Obama and Romney drew 67.2 million TV viewers, Nielsen said.